Bacterial resistance to β-lactam antibiotics, especially in Gram-negative bacteria, is most commonly mediated by β-lactamases. β-lactamases are enzymes that catalyze the hydrolysis of the β-lactam ring, which inactivates the antibacterial activity of the β-lactam antibiotic and allows the bacteria to become resistant Inhibition of the β-lactamase with a BLI slows or prevents degradation of the β-lactam antibiotic and restores β-lactam antibiotic susceptibility to β-lactamase producing bacteria. Many of these β-lactamases are not effectively inhibited by BLIs currently on the market rendering the β-lactam antibiotics ineffective in treating bacteria that produce these β-lactamases. There is an urgent need for novel BLIs that inhibit β-lactamases that are not effectively inhibited by the current clinical BLIs (e.g. KPC, class C and class D β-lactamases) and that could be used in combination with β-lactam antibiotics to treat infections caused by β-lactam resistant bacteria.